Automatic ball-mill feeder



H. H. BURHANS.

AUTOMATIC BALL MILL FEEDER. APPLICATION FILED MAY29, 1920.

Patented 00's. 25, 1921.

INVENTOR EEBurhans A TTORNEVS UNITED STATES PATENT OFFICE.

HARRY H. BURHAN S, OF NEWARK, NEW JERSEY.

AUTOMATIC BALL-MEL FEEDER.

' Specification of Letters Patent.

Patented Oct. 25, 1921.

Application filed May 29, 1920. Serial No. 385,272.

' Feeders, of which the followin is a s ecification.

This invention relates to an automatic ball mill feeder. I

It has been found by experience and observation, during actual operation of rotary ore crushing ball mills, that there is a critical point of power consumption at which the highest operating 'efliciency is obtained and that this critical point of power con sumption may be maintained by varying the quantity of the feed. g

The object of the present invention is to maintain any rotary crushing or grinding device at the highest operating efficiency by automatically varying the quantity of the feed by the power consumed.

The invention further consists of the parts and the construction and combination of parts as hereinafter more fully described and claimed, having reference to the accompanfiing drawings, in which- T e figure represents a side elevation of a conventional type of ball mill illustrating the application of the invention.

Briefly the invention consists in providing any combination of devices whereby a rotary crushing or grinding machine is maintained at the point of highest operating e1":- ficic iey by automatically varying the quantity of the feed to the machine by the variation in the power consumed by the machine.

To do this successfully it must be recognized that there is a critical point of power consumption which clearly indicates the point of highest operating efficiency; that the machine may be kept at or near this point by varying the quantity of feed whenever the power consumption varies either way, cutting oil or lessening the quantity of feed whenever the power consumption drops suddenly which indicates that the mill is overfed; that in mills of this class the power consumed increases gradually until the point of highest operating efficiency is reached; and that any large increase above this quantity makes a sharp decrease in power consumption, indicating that the load in the mill is becoming a balanced load, a condition under which no useful work is done by the machine and which naturally requires less power. The device for which patent is claimed cuts oil or decreases the quantity of feed at the first indication of over feeding, as indicated by the sharp drop in power consumption, automatically resuming the feed when conditions in the mill are again normal. To clearly understand what this invention does it is necessary, first, to clearly understand what conditions are necessary for the operation of a ball mill at the highest efiiciency.

Qonsistencg of pulp mill.

The consistency of pulp in the mill must be such that the surface of the balls are completely coated with an adherent layer of pulp which will remain on the balls when they come in contact and thus be crushed rather than splashed aside. The thickness of the pulp is only limited by the ability to discharge and to allow free movement of the balls.

Pulp lead in the mill.

Ooerfeedivzg.

It will be noticed that as the feed is gradually increased the power consumption also increases up to a certain point where it falls ofi' abruptly. This is the point of critical power consumption and is only slightly above the ficiently. f, however, the feed is increased above this point of highest operating efficiency the mill rapidly fills up causing the free movement of the balls to be hindered and the balls become embedded in a quiele sand which then sticks to the inside circurrference of the mill, making a balanced load causing the power consumption to suddenly drop. In extreme cases the mill does not resume crushing for an hour afiter the feed lpoint of highest operating efis out off. The addition of water at this stage seems to help very little. Apparently the only thing to do is to keep the feed off until the mill slowly grinds itself out. Of course,

Methods of hand eeding.

In certain mills the operators cut their feed when the ammeter reading drops and even then a mill occasionally fills up. Should their attention wander, they do not catch the drop quick enough. In other mills the operator tells by the sound of the balls and generally has the feedofl' at least forty five minutes a shift. Again, it is common practice to set the feed so low that there is no danger of the mill filling up. Naturally the operator has an easy time but the mill is not crushing up to capacity.

The automatic feed employed in the present instance does exactly what the operator tries to do when ammeter readings are taken. It cuts the feed at the first excessive drop or rise in amperage and automatically resumes feeding when the mill is again operating under conditions of highest opcratingv efficiency; As its automatic action is so much more sensitive and so much more dependable it cuts the feed oftener and for shorter intervals and hence keeps the mill operating at highest operating efiiciency with a resultant increase in tonnage as well as the decrease in cost, owing to the fact that only a small portion of the operators time is needed.

One example of reducing the invention to practice is as follows :-A indicates the drum of a standard form of ball mill, 2 the bearing supports, 3 the spiral feeder, 4 the hopper to which the material to be crushed or ground'is delivered, and 5 the driving gear through which power is transmitted rom a pinion 6 secured upon the shaft of a main driving motor 7 Mounted adjacent to the hopper 4 is a feeding belt 8 and mounted above said belt is an ore bin 9, of suitable construction provided with an adjustable discharging gate 10. The feeding belt is in this instance driven by an electrio motor 11 and means have been provided for automatically opening or closing the circuit through said motor, when the ball mill is operating, thereby regulating the quantity of ore delivered by the feeder and maintaining the mill at the point of highest operating efliciency.

This is, accomplished in the following manner: 12 and 13 indicate the main in coming wires of the current supply, 14 the switch on the mill motor line 15, the starting box to the main motor line, and 16 and 17 the Wires connecting with the motor 7 which drives the mill. Connected with the wires 16 and 17 is a pair of wires 18 and 19 which pass through a switch 20, a suitable number of resistance coils 21 and a rela 22. This relay is preferably constructed on the lines of the retarded relay type and is provided for the purpose of automatically closing 'a local circut through wires 23 and 24 which in turn are connected with a solenoid magnet 25. This solenoid operates a switch 26 which opens or closes a circuit through a pair of wires 27 and 28 connected with the motor 11 or what may be termed the feed belt driving motor, current to supply said motor being secured from wires '29 and 30 connected with the main line wires 12 and 13 and passing through a switch 31.

In this relay 22 I provide a pair of magnets 32 and 33 controlling a circuit closing armature 34:. One of these magnets 32 is designed to attract the armature and close the circuit when the load decreases below a predetermined point and the other of said magnets 33 operating to close the circuit when the load increases above a certain predetermined polnt 'so that a unlform action 'is had. In other words, the magnets 32 and 33 while both operate the circuit closer, these magnets are controlled by the load, but one of the magnets is operated by an overload and the other by an underload.

In operation, with the switches 14, 20 and 31 closed, it can readily be seen that current is permitted to flow through the main mill motor and the feed belt drivin motor. The current flow through the mi motor, however, varies as previously described, in proportion to the quantity of ore handled, that 1s, there is a critical point of power consumption which clearly indicates the point of highest operating eificiency. The ball mill should be kept at or near'this point by cuttin off. or-lessening the quantity of ore delivered whenever the power consumption drops which drop in consumption indicates that the mill is being overfed. This. variation in current consumption affects the relay 22 and causes this to make or break the local circuit through the solenoid magnet which controls the switch 26 thereby opening or closing the circuit through the feeder motor 11 and consequently automatically controlling the quantitlyI of-ore delivered to the mill.

aving thus described my invention what I claim and desire to secure by Letters Patent is?- v 1. The combination with a rotary crushing or grinding device and a motor for driving the same, of a feeder connected with the device for delivering material to be ground or crushed, a motor circuit, and means in said circuit actuated by variations of power consumed in the motor independent of the motor speed for automatically varying the quantity of the feed.

2. The combination .with a rotar crushing or grinding device and a motor or driving the same, of a feeder connected with the device adapted to deliver the material to be ground or crushed, a second motor adapted to drive the feeder, circuits for both of said motors, and means in the circuit of the driving motor adapted to control the circuit of the feed motor, said means actuated by the current consumed in the first motor independent of the speed of the first motor for automatically opening or closing the circuit through the second motor.

3. The combination with a rotar crushing or grinding device and a motor or driving the same, of a feeder connected with the device adapted to deliver the material to be ground or crushed, and means actuated by variations of the power consumed by the grinding or crushin device independent of the speed of said evice for automatically varying the quantity of the feed.

4. The combination with a rotary crushing or grinding device and a motor for driving the same, of a feeder connected with the device adapted to deliver the material to be ground, a second motor adapted to drive the feeder, and means actuated by the current consumed in the first motor independnected to said motor to deliver energy thereto, magnetic means in the circuit of the first motor, and means in the circuit of the second motor adapted to be controlled by said mag netic means, said magnetic means being responsive to variations in the power consumed by the first motor independent of its speed, whereby its control of the circuit of the second motor will affect the quantity and delivery of the material to the receptacle.

6. A receptacle adapted to receive mate rial to be treated, a motor for driving said receptacle, a feed device adapted to deliver material to the receptacle, a motor for driving the feed device, electrical circuits connected to said motors, a magnetic device in the circuit of the first motor, and switching means in the circuit of the second motor controlled by the magnetic device, said magnetic device operating to open orclose said switching device in response to current variations within a definite range and consumed b the first motor independently of the spec HARRY H. BURHANS.

receive material to be 

